It is not easy to look after someone with a serious disability. Often, people with serious mental illness or a disability that impairs their ability to look after themselves, need family and friends to help them look after their affairs. What’s worse, you may panic about what will happen to their financial affairs if you die.
The biggest challenge is often looking after money. If they have money, a policy that may pay out, or maybe you or someone else is providing money, then there is a risk that someone may take advantage of them

SA Revenue Service (Sars) calls this a Type A Special Trust. : SARS defines this trust as one created solely for the benefit of a person or more than one person with a “disability”, as defined in the Income Tax Act, and which makes it impossible for that person or people to manage their own financial matters

https://www.gov.za/documents/income-tax-act-29-may-1962-0000

The trust has to be set up purely in favour of the disabled person – known as the beneficiary. In other words, there must be no benefit for the trustees (the people who run the trust), just the beneficiary.
The trust must be registered with Sars as a type A special trust that enjoys a favourable tax status. Trusts pay income tax at the highest tax rate of 45% making them suitable only for certain situations, but in the case of a special trust, the Income Tax Act provides for the same tax rates that apply to individuals. Marginal tax rates, applied on a sliding scale according to income, apply.
Trusts pay tax on the capital gains they make in full but special trusts, like individuals, enjoy an annual exclusion enabling them to limit or avoid this tax. Capital gains tax is a tax on the profit that you make when you sell an asset – typically it is paid on the difference between the base or starting value and the value you sold for, but you may also be able to deduct other costs incurred in acquiring an asset like property. Individuals and special trusts enjoy an annual capital gains tax exclusion that allows you to make R40 000 of capital gains without paying tax each year. Ordinary trusts do not enjoy this annual exclusion.
The founder of the trust does not have to be related to the disabled person.
The special trust should have at least three trustees and this means that when or if the founder of the trust dies, the remaining trustees can still able to look after the disabled person.
The founder of the trust may transfer money for the benefit of the disabled person by means of a donation or tax-free loan. Baines cautions that there are instances where there will be donations tax implications for the donor and you should get advice from a properly qualified tax professional on how to avoid or minimise this tax.

http://1of1privatecollection.co.za/fiduciaryandtax/special-trusts-for-minors-and-those-with-special-needs/